The CAMPAIGN and CANVAS have CHANNEL_* fields for all the channels except In-app - which is also being returned by the API.

"channel": (string) channel type of the message (as in, "email", "ios_push", "webhook", "content_card", "in-app_message", "sms"),

Campaign docs
Canvas docs

Can we have a CHANNEL_IN_APP field representing whether or not the channel for the campaign was in app?